The effects that internet-based social networking sites (SNS) have on the labour market have yet to be investigated. The purpose of this paper is to examine whether and in what way SNS are changing the nature of the relationships between employers on the one hand, and employees and job applicants on the other. By means of an online survey, information was collected about attitudes towards data security, self-marketing and career development. This study suggests that employees who use social networking sites as self-marketing tools aim to build a positive reputation and thus redress the asymmetrical information relationship with employers. The survey also shows that data security plays an important role.